Mean focal length of an aberrated lens

Author(s): Cosmas Mafusire and Andrew Forbes

Abstract:

“We outline an approach for the calculation of the mean focal length of an aberrated lens and provide closed-form solutions that show that the focal length of the lens is dependent on the presence of defocus, x-astigmatism, and spherical aberration. The results are applicable to Gaussian beams in the presence of arbitrary-sized apertures. The theoretical results are confirmed experimentally, showing excellent agreement. As the final results are in algebraic form, the theory may readily be applied in the laboratory if the aberration coefficients of the lens are known.”

Link to Publications Page

Publication: Journal of the Optical Society of America A
Issue/Year: JOSA A, Vol. 28, Issue 7, pp. 1403-1409 (2011)
DOI: 10.1364/JOSAA.28.001403

Three-dimensional holographic lithography by an iterative algorithm

Author(s): Joshua J. Cowling, Gavin L. Williams, Alan Purvis, Richard McWilliam, Jose J. Toriz-Garcia, Nicholas L. Seed, Florian B. Soulard, and Peter A. Ivey

Abstract:

“We have applied an iterative algorithm for hologram design with multiple output image planes arranged in close proximity to create continuous patterns within an imaging volume. These holograms have been designed for photolithography on three-dimensional surfaces. The influence of simulated image plane separation on the final image, and its suitability for lithography, is assessed. Results are presented and the most suitable case is demonstrated experimentally.”

Link to Publications Page

Publication: Optics Letters
Issue/Year: Optics Letters, Vol. 36, Issue 13, pp. 2495-2497 (2011)
DOI: 10.1364/OL.36.002495

Generation of an axially super-resolved quasi-spherical focal spot using an amplitude-modulated radially polarized beam

Author(s): Han Lin, Baohua Jia, and Min Gu

Abstract:

“An axially super-resolved quasi-spherical focal spot can be generated by focusing an amplitude-modulated radially polarized beam through a high numerical aperture objective. A method based on the unique depolarization pro perties of a circular focus is proposed to design the amplitude modulation. The generated focal spot shows a ratio of x∶y∶z=1∶1∶1.48 for the normalized FWHM in three dimensions, compared to that of x∶y∶z=1∶0.74∶1.72 under linear polarization (in the x direction) illumination. Moreover, the focusable light efficiency of the designed amplitude-modulated beam is 65%, which is more than 3 times higher than the optimized case under linear polarization and thus make the amplitude-modulated radial polarization beam more suitable for a wide range of applications.”

Link to Publications Page

Publication: Optics Letters
Issue/Year: Optics Letters, Vol. 36, Issue 13, pp. 2471-2473 (2011)
DOI: 10.1364/OL.36.002471

Generalized beam quality factor of aberrated truncated Gaussian laser beams

Author(s): Cosmas Mafusire and Andrew Forbes

Abstract:

“We outline a theory for the calculation of the beam quality factor of an aberrated laser beam. We provide closed-form equations that show that the beam quality factor of an aberrated Gaussian beam depends on all primary aberrations except tilt, defocus, and x-astigmatism. The model is verified experimentally by implementing aberrations as digital holograms in the laboratory.”

Link to Publications Page

Publication: Journal of the Optical Society of America A
Issue/Year: JOSA A, Vol. 28, Issue 7, pp. 1372-1378 (2011)
DOI: 10.1364/JOSAA.28.001372

Recursive wavefront aberration correction method for LCoS spatial light modulators

Author(s): J. García-Márquez, J.E.A. Landgrave, N. Alcalá-Ochoa, C. Pérez-Santos

Abstract:

“We present two accurate and relatively simple interferometric methods for the correction of wavefront aberrations of about 3 wavelengths (3λ) in spatial light modulators (SLMs) of the liquid crystal on silicon (LCoS) type. The first is based on a recursive use of a wavefront fitting algorithm in a Wyko™ interferometer, in which Zernike polynomials are employed as the basis functions. We show here that the successive use of only three measurements is required to obtain a peak-to-valley (PV) error as low as λ/10, with an uncertainty of λ/30, in the compensated wavefront. The second method makes use of the actual optical path difference (OPD) computed by the interferometer at each pixel of the image of the interferogram of the LCoS modulator (LCoS-M). From numerical interpolation of these OPD values we were able to assign the required OPD compensation at each pixel of the LCoS-M. With this method, PV errors of the compensated wavefront as low as λ/16, with an uncertainty of λ/30, were obtained for the entire LCoS-M, or of λ/33 for the disk that we used as the domain of the Zernike polynomials in the first method.”

Link to Publications Page

Publication: Optics and Lasers in Engineering
Issue/Year: Optics and Lasers in Engineering, Volume 49, Issue 6, Pages 743-748, (2011)
DOI: 10.1016/j.optlaseng.2011.01.024

Fraunhofer computer-generated hologram for diffused 3D scene in Fresnel region

Author(s): Yuan-Zhi Liu, Jian-Wen Dong, Yi-Ying Pu, He-Xiang He, Bing-Chu Chen, He-Zhou Wang, Huadong Zheng, and Yingjie Yu

Abstract:

“A Fraunhofer computer-generated hologram (CGH) is proved to be valid in display for three-dimensional (3D) objects from the Fresnel to the far-field region without a Fourier lens for reconstruction. To quickly compute large and complicated 3D objects that consist of slanted diffused surfaces in the Fresnel region, a Fraunhofer-based analytical approach using a basic-triangle tiling diffuser is developed. Both theoretical and experimental results reveal that Fraunhofer CGH can perform the same effects as Fresnel CGH but require less calculation time. Impressive 3D solid effects are achieved in the Fresnel region.”

Link to Publications Page

Publication: Optics Letters
Issue/Year: Optics Letters, Vol. 36, Issue 11, pp. 2128-2130 (2011)
DOI: 10.1364/OL.36.002128